The present invention relates to a method and a device for activating the display of at least one stall margin indicator of an aircraft, in particular of a transport airplane.
In order to reinforce the vigilance of crew members to aircraft stall situations, it is known practice to use stall margin indicators. The stall margin information is supplied to the pilots via a permanent display on their primary attitude instruments.
It is known practice to use a chevron centered on a primary flight readout, which indicates the stall margin and the direction of the aircraft recovery maneuver in the case of a stall. A stall margin indicator is also known that takes the form of markers situated laterally on the same type of readout. The stall margin of these two representations is materialized by the distance between the bottom point of the symbol or symbols and the model of the aircraft, centered on the primary flight readout.
The stall margin indicators complement the existing stall indicators, the presence of which is dictated by the regulations. In the symbology employed, the stall margin indicator is a piloting symbol completely apart. Because of this and even more than what may be required of a text message or an audio alert, the information transmitted by this symbol has to be very accurate, to make it possible to perform an emergency maneuver when that proves necessary.
The stall margin indicator allows prevention or else involves an immediate corrective action to reduce the angle-of-attack of the aircraft on the part of the pilot when the stall margin decreases dangerously or becomes zero. The need for a preventive or corrective maneuver is however required only if the incidence of the aircraft is no longer protected by the usual systems, because the pilots can use the full authority of their stick without the risk of exceeding the aircraft's stability limits